Pulse generator



wuosQm Sept. 24, 1963 F. B. ANDERSON ETAL PULSE GENERATOR Filed Jan. 27,1959 MUQSOW suw/ QSSR B. ANDERSON WVENTORSs H PEARSALL, JR.

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ATTORNEY United States Patent 3,105,169 PULSE GENERATGR Frithiof B.Anderson, Winston-Salem, N.C., and Samuel H. Pearsall, In, Donelson,Tenm, assignors to Bell Telephone Laboratories, Incorporated, New York,

N.Y., a corporation of New York Filed Jan. 27, 1959, Ser. No. 789,445 5(Ilaims. (Cl. 315-166) This invention relates to pulse circuits and,more particularly, to pulse circuits employing gaseous electrondischarge devices.

In a wide variety of electronic equipments, for both operating andtesting purposes, there is a need for accurately timed pulse signals ofprecise duration and of substantial magnitude. This widespread need hasgiven rise to a large number of difierent generators for such pulsesignals. In a broad group of these generators, energy has been passedthrough one path for storage at a high level in a suitable reservoir.Thereafter, at a desired instant this stored energy is released througha different path. conventionally, one of these paths includes autilization apparatus, and the shift between storage and release circuitstates marks the beginning and ending, though not necessarily in thatorder, of a desired pulse signal.

Advantageously in this type of apparatus, electron tubes have beenemployed as accurately timed switching devices tor shitting storageenergy between a charging path and a discharge path. Commonly, vacuumtubes may be so employed but with the limitation that, as the amplitudeof the required pulse signal current rises, both the size and heatingpower requirements of the necessary vacuum tubes may go beyond thatwhich is feasible for a particular application.

In such circumstances advantageous resort may be made to gaseouselectron discharge devices which are exemplified by the well-knownthyratron tube. In these discharge devices'ionized gas within anenvelope serves as a current carrier between cathode and anodeelectrodes. As is well known in the art, the initiation of such acurrent conducting ionized condition may be controlled by an auxiliarygrid electrode. Thereafter, heavy current may be conducted by theionized gas particles Within the envelope without necessitating heavythermionic electron emission by a cathode.

Utilization of such gaseous electron discharge devices in the past,however, has been limited to pulse signal generators in which the timingof one portion of the pulse signal, for example, the terminatingportion, is of relative unimportance. This limitation has resulted fromthe fact that, once an appropriate conduction condition has beenestablished within these gaseous devices, the electrostatic effect ofauxiliary grids becames insignificant compared to that of the currentconducting ionized particles. Hence, termination of a current conductingelectron discharge through such ionized devices becomes de pendent uponexternal circuit phenomena almost entirely, and the discharge conductioncurrent 'alone has, to a great extent, governed its own termination.

Accordingly, pulse generators of the prior art, on the one hand, haverequired overlarge vacuum tubes and associated power supplies or, on theother hand, have been objectionably inaccurate in either the beginningor the terminating portion of generated pulse wave signals. This latterinaccuracy has often led to a further objectionable delay in thegeneration of succeeding pulse signals.

It is a principal object of the present invention to generate accuratelytimed pulse signals of well-defined wave form, of substantial amplitude,and of rapid recurrence rate.

hid-5J5? Patented Sept. 24, 1963 It is a further object of the presentinvention to simplify and to reduce the cost of pulse generatingstructures.

In accordance with the present invention these and other objects areachieved with a structure in which two gas-filled electron dischargedevices are arranged in serial connection with each other and with anenergy storing reservoir. A control signal applied to one of thesedevices establishes heavy current conducting discharge conditionstherein to initiate an abrupt change of substantial magnitude in anoutput signal. This control signal, applied at a later time, establishesa like discharge condition within the other device to accelerate thetermination of the conducting discharge in both devices by theirdeionization and to terminate an output pulse signal by bypassing theparallel connected load circuit in Which the output signal appears.

The control discharge devices are advantageously gaseous dischargedevices having a control or starter electrode or grid to which thecontrol signal is applied; a thyratron is an example of this type ofdevice. Such devices enable the circuit to provide a large outputsignal. Circuits in accordance with our invention are so arranged thatconduction in the control gaseous discharge devices is terminated by thebreakdown of the last of the control devices, conduction in this lastdevice automatically extinguishing the conduction in itself and in anyother such devices in the circuit in a high conduction state at thattime.

In one specific illustrative embodiment wherein the storage capacitor ispriorly changed, as through a gaseous discharge device of the thyratrontype, the circuit is arranged so that the first control deviceestablishes a series circuit including itself, the storage capacitor,and the load to initiate the output pulse through the load. A secondcontrol device, upon conduction, bypasses the load and establishes aseries path including itself, the storage capacitor, and the firstdevice, to discharge the capacitor and in so doing to extinguishconduction both in itself and in the first device. Accordingly, thefirst and second control gaseous discharge devices are mutually poledfor the flow of current in one direction through the series pathincluding the intermediately connected storage condenser.

In a second illustrative embodiment the first device controls thecharging of the storage capacitor and also determines the initiation ofthe output pulse. The second control gaseous discharge device terminatesthe output pulse by bypassing the output circuit, and a third gaseousdischarge device connected in parallel with the storage condenser uponbreakdown discharges the storage condenser and thereby automaticallyextinguishes the discharge in itself and in both the other controldevices.

It is a feature of this invention that a pulse generator circuit forproducing accurately timed large amplitude output pulses includes a pairof control discharge devices series connected with a storage capacitorfor passage of current through this series path in a single direction.More specifically in accordance with our invention, the controldischarge devices are gaseous discharge devices as of the thyratron typehaving a control or starter electrode.

It is another feature of our invention that the breakdown of one suchcontrol discharge device both discharges the storage capacitor and in sodoing extinguishes or disables both itself and any other conductingcontrol discharge device.

It is a further feature of one specific illustrative embodiment of ourinvention that the storage capacitor be charged independently of the twocontrol gaseous discharge devices set forth above, the two devices beingconnected so that uponconduction of the second to terminate the outputpulse, both devices are initiallycod ducting providing low impedanceconnections to ground in a series circuit from both plates of thestorage capacitor and thereby providing both automatic discharge of thecapacitor and extinction of the discharge in both control devices.Further in accordance with our invention,'in this specific embodimentthereof the charging of the storage condenser may be controlled throughanother gaseous discharge device having an inductance connectedin'series therewith, conduction in this device being selfextinguishingon the charging of the storage condenser.

A complete understanding of this'invention and of these and otherfeatures thereof may be gained from con. sideration of the followingdetailed description together with the accompanying drawing, in which:

FIG. 1 is a schematic diagramof an illustrative high power pulsegenerating system in accordance with one embodiment of the invention;

FIG. 2 is a schematic diagram of another illustrative high power pulse,generating system in accordance-with ing the operations of theembodiments of the invention as shown in FIGS. 1 and 2, respectively.

7 Referring now more particularly to the drawing, in FIG. 1 there isshown a resonantly charged pulse generating circuit to which energy issupplied from a direct energy source 11 which may conveniently be anyone of the many direct current power supplies known in the electronicart. Energy from this source serves to charge a storage element, thecapacitor 12, through a serially connected charging inductor 14 and avariable impedance isolating element 16 which adv-antageouslymay be ahigh conductance electron discharge device such as a thyratron electrontube. Completing a serial circuit including the capacitor 12 and theenergy source 11 is a rectifying device comprising a diode-connectedtriode electron tube 18, which is connected across a pair of outputterminals 17 and 19 and is poled ior conducting current in a lowresistance direction consistent with the polarity of the sourcell.

A load impedance 20 is connected in parallel with electron tube 18. Thisload impedance 20 is shown for convenience of illustration as aresistor. It may as well be any pulse utilization circuit as, forexample, a radar magnetron pulsing circuit. I

Two circuit controlling electron discharge devices 22 and 24 areconnected in serial relation with the storage capacitor 12, each forconducting current flowing through that capacitor in a like direction.These discharge devices may advantageously also be thyratron'tubes. Inaccordance with the above-noted serial connection these thyratron, tubesare connected anode to cathode.

to promote heavy current conduction. Thyratron 22 is further connected,as shown, in serial relation with the energy source 11, the inductor 14,and the isolating thyratron 16. The other circuit controlling dischargedevice,

thyratron 24, is further connected in parallel with the load impedance20.

As shown, the control grids of the three thyratrons 16, 22, and 24 arerespectively connected through resistors 26, 27, and 28 to a source ofOff-biasing potential 30.

Each has a 7 direct connection of its shield grid to its cathodeelectrode supplied to the control grid of thyratron 16 by a directconnection, to the control grid of the thyratron 22 through a delay line34, and to the control grid of the thyratron 24 through both the delayline 34 and an additional delay line 36. These delay lines may be anyone or the many such delay lines well known in the art. They may,

for example, be serially connected 1r sections of inductors andcapacitors having values chosen to yield delay times corresponding tothe intervals t -t and t t The magnitude of these intervals can best beconsidered together with a discussion of the operation of the pulsegenerator of FIG. 1 which may be understood more clearly Iby aconsideration of the wave forms shown in FIG. 3.

Assuming the capacitor 12 to be initially discharged, the Oft biasingpotential source 30 renders each of the thyratrons 16, 22, and 24 in .anon-conducting, deionized state, The circuit stands in a quiescentstate, and no signal appears across the load impedance 20; accordingly,as indicated in FIG. 3, the output signal voltage E is zero.

A positive pulsesignal of suitable amplitude is generated by the timingpulse source 32 Hit a time designated t This positive pulse drives thecontrol grid electrode of the isolating thyratron 16 to ionize the gasparticles within that discharge device. Thus, an electrical circuit iscompleted through the electron tube 18, which acts to bypass theloadim-pedance, the capacitor 12, the

thyratron 16, and the inductor 14 to the energy source 11. At thisinstant 1 a voltage E appears across the inductor with a polarity asindicated by the arrow and I in magnitude almost equal to and opposingthe energy source potential E This situation is shown in FIG. 3 at timet by referring to the curve designated in this figure as E a r l 7Immediately afiter the instant t the storage capacitor 12 potential Erises as the capacitor is charged through the electron tube 18. 'Theinductor voltage E meanwhile decays sinusoidally to a negative value atthe instant t The capacitor potential E correspondingly increasessinusoidally to a value substantially above the energy source potentialat this same instant 1 Indeed, by well-known circuit analysis it may beshown that if the charging path, including the electron tube 18, thecapacitor 12, the thyratron 16 and the inductor 14 are all of zeroresistance, the capacitor voltage E rises to a value just twice thepotential of the energy source 11. At this instant the thyratron 16 isdeionized by the current through it reducing to zero, and the energysource 11 is thus isolated from the capacitor and its associatedelements.

The time interval required for the capacitor 12 to rise to this maximumpotential, that is, the interval t t is given by half the period of thenatural resonant one of these three tubes at a different time, whichtimes are designatedt t and 1 in FIG. 3. The pulses are frequency ofthe'inductor 14 and the capacitor 12. Denoting the inductance andcapacitance values of these two elements as L and C, respectively, it isreadily ap parent that in this preferred illustrative embodiment of theinvention the time t .t is given by the expression Accordingly, delayline 34 is constructed to delay pulse signals applied thereto from thepulse source 32 by just this interval -4 as given above.

As shown in FIG. 1, a pulse signal delayed by delay line 34 is appliedto the Off-biasing control electrode of the thyratron 22 at thisadvantageous instant t the pulse may, however, be app-lied at anyreasonable time thereafter as the capacitor tends to maintain itscharge. The Off-biasing potential applied to this latter thyratron 22 bythe biasing source 30 is thus overcome and the thyratron is enabled asan ionized current conducting condition is established. Ion supporteddischarge current now flows from the storage capacitor 12 through thelow impedance path presented by this thyratron 22. Meanwhile thethyratron 16 is deionized and disabled by the equality of the capacitorpotential E with the sum of the inductor potential E and the energysource potential E Thus, the biasing potential source 30, acting throughthe resistor 26, re-establishes its Oil-biasing control of the isolatingthyratron 16. As the now isolated capacitor begins discharging throughthe thyratron 22, its potential drops and current tends to flow throughthe load resistor 20 to support the discharge in the thyratron 22. Thisdischarge current in the load impedance 20 appears as a sharpnegative-going pulse indicated by the heavy curve designated B in FIG.3.

As the energy stored in the capacitor 12 decays at an exponentiallydecreasing rate, the output signal appearing across the load impedance20 tends to have a substantial value for an indefinite period. Thisfollows from the fact that the discharge thyratron tends to remainionized as long as the capacitor is capable of supplying substantialcurrent thereto.

In accordance with an aspect of our invention, the third thyratron 24provides for the termination of the output signal. This third thyratrontube 24 is connected in serial relation with the discharge thyratron 22and the storage capacitor 12 to provide a complete series path for theflow of the capacitor discharge current. This third thyratron is also,as shown, connected in parallel with the load impedance 20. At a desiredpulse termination time t the pulse from the timing source 3-2 is appliedthrough the delay lines 34 and 36 to overcome the Cit-biasing potentialsupplied by the source 30 through the resistor 28. Thus, the thirdthyratron 24 is enabled and discharge current for the capacitor flowsthrough the very low impedance path provided by the two ionizedthyratrons 22 and 24. Immediately the thy ratron 24 is ionized, the loadimpedance 20 is efiectively shont-oircuited to terminate the outputpulse and the capacitor is rapidly discharged through a near zeroimpedance path provided by the two ionized thyratrons 22 and 24. Thecapacitor being discharged rapidly, the ionizing potential for thesethyratrons is rapidly removed and they both are returned to anonconducting condition in expeditious fashion to await a repetition ofthe above described operation to generate a new high current pulse inthe load impedance 20.

Turning attention now to the pulse generator delineated in FIG. 2, thereis seen another illustrative embodiment of the principles of theinvention. In this embodiment, shown in FIG. 2, elements correspondingto those of FIG. 1 are correspondingly numbered.

In this generator a first gaseous electron discharge device 46, whichmay advantageously be a thyratron, is serially connected with thestorage capacitor 12 and a load impedance 20*. A second gaseous electrondischarge device 54, again advantageously a thyratron, is connected inserial arrangement with the first discharge device 46 and the capacitor12. This capacitor is of a 'value to have, in conjunction with the loadimpedance 20, a charging time constant which is large compared with thedesired pulse signal duration. Still a third gaseous discharge device,thyratron 52, is connected in parallel with the storage capacitor and inserial relation with the first and second discharge devices 46 and 54.

A control grid electrode of each of these three thyratrons '46, 52, and54 is connected through resistors 26, 27, and 28, respectively, to asource of Off-biasing potential 30. Energy source 41 is connected asshown with a polarity to supply energy to the capacitor 12 in adirection consistent with a high conductance condition of the seriallyconnected discharge devices 46, 52, and 54. A timing pulse source 32supplies intermittent positive enabling pulses to the control electrodesof the thyratrons 46, '52, and 54 at successive instants of time t t andt;, by virtue of the operation of delay lines 34 and 36 as shown.

The operation of this embodiment of the invention can readily beunderstood with reference to the wave forms of FIG. 4. Upon generationof a timing pulse from the source 32 at a time t the Off-biasingpotential applied to the thyratron 46 is overcome. Accordingly, thisthyratron is conditioned for heavy discharge conduction and thecapacitor 12 is charged by the energy source 41 through the loadimpedance 20 connected between a pair of output terminals 17 and 19.Accordingly, an output pulse signal B immediately appears across thisload impedance. This output signal, as indicated in FIG. 4. has a valuesubstantially corresponding to the potential E in view of the largecapacitance of the capacitor 12 and the virtually zero impedance of theconducting thyratron 46.

At the instant t later than t by an interval which is governed by thedelay line 34, the second of the serially connected discharge devices,the thyratron 54, is driven into an ionized discharge condition by thearrival of the positive pulse from the source 32. This thyratron, byvirtue of its parallel connection with the load impedance 20, acts tobypass the load impedance and to terminate the output pulse E Thecapacitor 12 now is almost immediately charged to the full potential ofthe energy source 41 and the two discharge devices 46 and 54 aremutually driven by the heavy conduction of the second discharge deviceto a deionized condition.

At a still later instant t later than t by an interval governed by thedelay line 36, the pulse from the source 32 arrives at the control gridof the third thyratron 52 to condition this thyratron for dischargeconduction. Hence, the energy stored in the capacitor 12 is dissipatedrapidly and the pulse generator is restored to a quiescent conditionawaiting the generation of a new enabling pulse from the source 32.

While specific illustrative embodiments of this invention have beendescribed herein, it is, of course, to be understood that theabove-described arrangements are merely illustrative of the applicationof the principles of the invention. Thus, numerous other arrangementsmay be devised by those skilled in the art without departing from thespirit and scope of the invention.

What is claimed is:

1. Pulse generating apparatus comprising a storage capacitor, electricalenergy source means for charging said capacitor, a pair of terminals forconnection of a load impedance, said capacitor, said source means, andsaid load impedance terminals being connected in serial arrangement,first and second gaseous discharge devices connected in serialarrangement for current conduction in a like circuit direction, saidfirst discharge device being connected to one side of said capacitor andbeing pole-d for current conduction in a direction consistent with thepolarity of said source, said second discharge device being connected tothe other side of said capacitor and across said terminal pair, meansfor normally biasing said first and second discharge devices in anon-conducting condition, means for applying an enabling trigger signalto said first discharge device to establish a current conductioncondition therein to alter the charge state of said capacitor throughsaid load impedance, and means for thereafter applying said triggersignal to said second device for establishing a conduction conditiontherein for bypassing said load impedance terminals and for acceleratingthe re-establishment of a non-conducting condition in said first device.

-2. A pulse generator which comprises an electrical energy storageelement, first and second gaseous electron discharge devices, a distinctseries circuit comprising said storage element and said first and seconddischarge devices being mutually poled for current conduction in a likecircuit direction through said storage element, a load impedance, anenergy source connected for charging said storage element with apolarity to drive current through at least one of said dischargedevices, biasing means for maintaining said discharge devices in anormally nonconducting condition, means for applying a trigger pulsesignal to said first device forestablishing'a discharge conditiontherein for altering a current flow condition in said load impedance,and means for thereafter applying said trigger pulse signal to saidsecond device to-establish a discharge condition therein foraccelerating the dis establishment of the discharge condition in saidfirst device. 3. Apparatus as set forth in claim 2 wherein said firstand second discharge devices are connected in parallel with said loadimpedance.

4. Apparatus for applying electrical energy from a source as an energypulse to a load,'said apparatus comprising a storagetcapacitor havingone terminal connected to a first gaseous electron discharge device andthe other terminal connected to a second gaseous electron dischargedevice, said first and second discharge devices being connected in shuntwith the load, a distinct series circuit including said storage elementand said first and second discharge devices mutually poled in a likedirection, biasing means for maintaining said discharge devices in anormally deionized or nonconducting condition, means for applying anionizing trigger signal to said first de-- vice for establishing adischarge condition therein to initiate a current pulse in the load, andmeans for thereafter applying said ionizing trigger signal to saidsecond device for establishinga discharge condition therein to terminatethe pulse in said load and to accelerate the disestablishment of thedischarge conditionsin said first and second devices.

'5. In a pulse generator which comprises an electrical energy storageelement, a load impedance, means including an energy source for chargingsaid storage element, a firs-t gaseous discharge device series connectedbetween said charging means and said storage element, means fortriggering said first gaseous discharge device to inio tiate saidcharging of said storage element, a second gaseous discharge deviceconnected to said storage ele: ment so as to define a series fpaththerewith and with said load impedance, and means for triggering saidsecond References Cited in the file of this patent V UNITED STATESPATENTS 2,470,895 Marlowe May 24, 1949 2,596,142 GerWin May 13, 19522,677,053 Nirns Apr. 27, 1954 2,709,746 Page May 31, 1955 2,710,351Lebacqz June 7, 1955 2,752,500 1 Bruyning June 7, 1956 2,793,290 WagnerMay 21, 1957 V FOREIGN PATENTS 454,678 Canada Feb. 15, 1949 OTHERREFERENCES Graydon: The Application of Pulse Forming Networks,Proceeding of the National Electronic Conference, vol. XII, 1956, pp.1071-1075.

1. PULSE GENERATING APPARATUS COMPRISING A STORAGE CAPACITOR, ELECTRICALENERGY SOURCE MEANS FOR CHARGING SAID CAPACITOR, A PAIR OF TERMINALS FORCONNECTION OF A LOAD IMPEDANCE, SAID CAPACITOR, SAID SOURCE MEANS, ANDSAID LOAD IMPEDANCE TERMINALS BEING CONNECTED IN SERIAL ARRANGEMENT,FIRST AND SECOND GASEOUS DISCHARGE DEVICES CONNECTED IN SERIALARRANGEMENT FOR CURRENT CONDUCTION IN A LIKE CIRCUIT DIRECTION, SAIDFIRST DISCHARGE DEVICE BEING CONNECTED TO ONE SIDE OF SAID CAPACITOR ANDBEING POLED FOR CURRENT CONDUCTION IN A DIRECTION CONSISTENT WITH THEPOLARITY OF SAID SOURCE, SAID SECOND DISCHARGE DEVICE BEING CONNECTED TOTHE OTHER SIDE OF SAID CAPACITOR AND ACROSS SAID TERMINAL PAIR, MEANSFOR NORMALLY BIASING SAID FIRST AND SECOND DISCHARGE DEVICES IN ANON-CONDUCTING CONDITION, MEANS FOR APPLYING AN ENABLING TRIGGER SIGNALTO SAID FIRST DISCHARGE DEVICE TO ESTABLISH A CURRENT CONDUCTIONCONDITION THEREIN TO ALTER THE CHARGE STATE OF SAID CAPACITOR THROUGHSAID LOAD IMPEDANCE, AND MEANS FOR THEREAFTER APPLYING SAID TRIGGERSIGNAL TO SAID SECOND DEVICE FOR ESTABLISHING A CONDUCTION CONDITIONTHEREIN FOR BYPASSING SAID LOAD IMPEDANCE TERMINALS AND FOR ACCELERATINGTHE RE-ESTABLISHMENT OF A NON-CONDUCTING CONDITION IN SAID FIRST DEVICE.